Feeding questions

Regan is a draft cross and I have read so much about EPSM I wonder if I need to do some dietary changes. She is a 4 year old Clyd./TB and doesn't have a lot of signs of EPSM but is doing some things that could be related. The biggest thing I have noticed is that she is sore in the hind end, won't pick up the left canter lead, seems to be rough in the trot instead of smooth (she won't lengthen) and she holds her left hind leg at rest (she just doesn't put a lot of weight on it but by no means is holding it up off the ground). She has actually even fallen twice in the past two weeks while I was riding her. She got up and continued but it certainly set off the alarms. Anyway, she is on Orch./Alph. hay, Safe Choice and lots of pasture time. She isn't loosing weight and really doesn't get much grain (about 1/2 a scoop per day). She was putting on too much weight and that is why she was cut back so far on the grain. I worry about her getting enough fat in her diet and if I need more then what do I do so that she doesn't put on too much weight? She is out at night and only in during the day because it is just down right too hot here in Atlanta. I have not been great about exercising her everyday and probably need to do more. Anyway, just curious what you guys thought. I have read the Rural Heritage Vet Clinic articles but again I am worried about increasing her grain too much. Any thoughts? Oh, I have talked with my vet about the soreness in the hind end and he agreed and said to try message and working her over some poles and small cross rails. (This was before the other stuff started popping up) Thanks!!!